Piston cooling jets or oil injectors may be implemented in an engine to provide engine cylinder cooling. In particular, each oil injector sprays oil onto an underside of a corresponding piston to create a cooling effect on the piston. Furthermore, the oil propagates from the underside of the piston to the surrounding walls of a corresponding engine cylinder as the piston reciprocates in the engine cylinder to provide a cooling effect to the combustion chamber. In one example, operation of an oil injector occurs when the oil pressure in the engine is sufficient to overcome a pressure level of a check valve in the oil injector assembly. As long as the oil pressure is greater than the pressure level of the check valve the injector injects oil onto the piston.
However, the inventors have recognized several potential issues with such a configuration. For example, since operation of the oil injector is merely based on the pressure setting of the check valve in the oil injector assembly, the amount of oil that is injected by the oil injector cannot be adjusted to accommodate different operating conditions. In one example, if the check valve pressure level is set too high, then the oil injector operates less frequently and cooling is reduced resulting in increased engine knock that reduces drivability or pre-ignition that degrades the engine.
In another example, if the check valve pressure level is set too low, then the oil injector operates more frequently and additional oil above and beyond what is suitable for engine cylinder cooling is provided to the engine cylinder. The additional oil increases oil consumption and forms more oil deposits in the combustion chamber. The oil deposits have an insulating effect that slows the transfer of heat away from the combustion chamber and contributes to engine knock and/or pre-ignition.
In one example, the above mentioned issues may be addressed by a method for operating an engine including an oil injector injecting oil onto a piston of the engine, comprising, adjusting oil injection in response to an indication of pre-ignition. By adjusting oil injection, suitable cooling effects can be provided without providing additional oil that increases the amount of oil deposits in the engine. In this way, the risk of pre-ignition can be reduced.
Moreover, this approach allows for oil injection to be controlled more precisely than mere binary operation of previous implementations. As such, oil injection can be adjusted differently to accommodate different operating conditions. For example, oil injection can be adjusted by a first amount in response to an indication of pre-ignition and oil injection can be adjusted by a second amount different from the first amount in response to an indication of engine knock.
It will be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description, which follows. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined by the claims that follow the detailed description. Further, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.